Trends in Cancer Incidence in Maputo, Mozambique, 1991–2008

RESEARCH ARTICLE
Trends in Cancer Incidence in Maputo,
Mozambique, 1991–2008
Cesaltina Lorenzoni1,2, Alba Vilajeliu3,4, Carla Carrilho1,2, Mamudo R. Ismail1,2,
Paola Castillo3, Orvalho Augusto5, Alberto L. García-Basteiro3,7, Mohsin Sidat5, Silvia de
Sanjosé6, Clara Menéndez3,7, Jaume Ordi3,8*
1 Department of Pathology, Maputo Central Hospital, Maputo, Mozambique, 2 Faculty of Medicine, Eduardo
Mondlane University, Maputo, Mozambique, 3 ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital
Clínic—Universitat de Barcelona, Barcelona, Spain, 4 Department of Preventive Medicine and
Epidemiology, Hospital Clinic, Universitat de Barcelona, Barcelona, Spain, 5 Department of Microbiology,
Faculty of Medicine, Eduardo Mondlane University, Maputo, Mozambique, 6 Unit of Infections and Cancer,
Institut Catala d'Oncologia, L'Hospitalet de Llobregat, Barcelona, Spain, 7 Centro de Investigação em Saúde
de Manhiça (CISM), Maputo, Mozambique, 8 Department of Pathology, Hospital Clinic, Universitat de
Barcelona, Barcelona, Spain
* [email protected]
Abstract
Background
OPEN ACCESS
Citation: Lorenzoni C, Vilajeliu A, Carrilho C, Ismail
MR, Castillo P, Augusto O, et al. (2015) Trends in
Cancer Incidence in Maputo, Mozambique, 1991–
2008. PLoS ONE 10(6): e0130469. doi:10.1371/
journal.pone.0130469
Academic Editor: Aamir Ahmad, Wayne State
University School of Medicine, UNITED STATES
Very limited information is available regarding the incidence of cancer in sub-Saharan
Africa. We analyzed changes in cancer patterns from 1991 to 2008 in Maputo
(Mozambique).
Methods
We calculated the rates of incidence of different cancer sites by sex in the 5-year age-group
of the population of Maputo city as well as age-standardized rates (ASRs) and average
annual percentage changes (AAPC).
Received: January 5, 2015
Accepted: May 20, 2015
Results
Data Availability Statement: All relevant data are
within the paper.
Over the 18-year study period a total of 12,674 cases of cancer (56.9% females) were registered with an overall increase in the risk of cancer in both sexes. In males, the most common
cancers were those of the prostate, Kaposi sarcoma (KS) and the liver. Prostate cancer
showed the most dramatic increase over the whole study period (AAPC +11.3%; 95% CI:
9.7–13.0), with an ASR of 61.7 per 105 in 2003–2008. In females, the most frequent cancers
were of the uterine cervix, the breast and KS, with the former increasing along the whole
study period (AAPC + 4.7%; 95% CI: 3.4–6) with an ASR of 62.0 per 105 in 2003–2008 as
well as breast cancer (AAPC +6.5%; 95%CI: 4.3–8.7).
Funding: The authors have no support or funding to
report.
Conclusions
Competing Interests: The authors have declared
that no competing interests exist.
Overall, the risk of cancer rose in both sexes during the study period, particularly among
cancers associated with westernization of lifestyles (prostate, breast), combined with
Published: June 25, 2015
Copyright: © 2015 Lorenzoni et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
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Trends in Cancer Incidence in Mozambique
increasingly rising incidences or limited changes in cancers associated with infection and
poverty (uterine cervix, liver). Moreover, the burden of AIDS-associated cancers has shown
a marked increase.
Introduction
Knowledge of cancer patterns in the different populations is crucial to guide preventive efforts
[1–4]. For this reason, cancer registries have been developed to record epidemiological data
that are used to guide cancer prevention and control programs [1–5]. Unfortunately, very limited information is available regarding the incidence of cancer in sub-Saharan Africa[1,4–6].
This may be due to different reasons including limited resources in collecting and registering
information as well as the lack of stability in maintaining registries over long periods of time.
All of this has precluded evidence-based analysis of time patterns related to the incidence of
cancer in this region[4,7,8].
After the end of the civil war in 1991 the Department of Pathology of the Maputo Central
Hospital (MCH) started a cancer registry with the aim of obtaining information on the occurrence of cancer in the population of Maputo city. This lengthy registration of data has provided
a unique opportunity to study temporal trends in cancer patterns in an African setting.
Interestingly, epidemiological data had previously been obtained by the Department of
Pathology of the MCH (then known as Miguel Bombarda Hospital) from 1956 to 1961 in a
cancer survey covering the metropolitan area of 60 square kilometers of Maputo (then known
as Lourenço Marques) [9].
More than 50 years later, significant social and epidemiological changes have taken place in
Mozambique, with a progressive urbanization of the population and the eruption of the HIV
epidemic which has disproportionately affected many sub-Saharan African countries[9].
In the present study we analyzed the changes in cancer patterns in Maputo city, Mozambique from 1991 to 2008.
Materials and Methods
Study Site
This study was performed in the Department of Pathology of the MCH, a 1500-bed hospital
that is the only quaternary care center in Mozambique and is a national referral center. This
department primarily serves the Southern Zone of Mozambique including Maputo and its surroundings (provinces of Maputo, Gaza and Inhambane), with a small proportion of cases
derived from other areas of the country due to the national referral nature of the institution.
The department receives virtually all specimens from the city of Maputo. The department has a
database of all the samples received for pathological diagnosis including specimens of most
types of cancers (with the exception of leukemia and cancers with only a clinical diagnosis).
Study Design
This study was approved by the National Bioethics Committee of Mozambique, and the
Mozambican Ministry of Health (Ref. 389/CNBS). The analysis included all the cases of cancer
registered in the Department of Pathology of the MCH from January 1, 1991 to December 31,
2008. Data were entered into a Microsoft Access database (Microsoft Co, Redmond, WA,
USA) which, upon data entry, prevents the use of nonexistent codes and performs checks for
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Trends in Cancer Incidence in Mozambique
internal consistency between variables. The database was carefully reviewed (name, age) to
confirm that no duplications had been registered. Information about previous analyses in the
same patient was also obtained, in order to identify potential duplicate registrations. Cases
were identified in the registries as histological studies (including biopsies and surgical pathology), cytological specimens, and autopsies. For each case identified basic demographic data
were collected, including age, sex and address. Patients from sites other than Maputo were
excluded. For each specimen, the date of diagnosis, method of diagnosis, site from which the
specimen was taken (topography), and microscopic morphology were recorded. Patient records/information were anonymized and de-identified prior to analysis. All topographic and
morphologic classifications were made according to the International Classification of Diseases
for Oncology (ICD-O)[10,11] and were converted into the 10th version of the ICD[12]. In concordance with other cancer registries, cancers such as Kaposi’s sarcoma and malignant lymphomas were not classified by localization, as they are considered multifocal, and were
included only once in the analysis[5,7]. Multiple cancers occurring in the same patient were
entered as separate cases. Squamous cell carcinomas (SCCs) of the conjunctiva were defined as
tumors with ICD-O morphology codes M8010–M8082 of conjunctiva ICD-O C69.0) or eye,
unspecified (ICD-O C69.9).
Population
Censuses of the population of Mozambique were performed in 1980[13], 1997[14] and 2007
[15], providing demographic information of Maputo by sex and 1 year of age groups for these
years. Intercensal estimates were calculated assuming a constant rate of change in growth
within sex and age groups. Fig 1 shows the population of Maputo by gender and age groups in
the censuses of 1997 and 2007.
Statistical Analysis
The rates of incidence of cancer were calculated for the 5-year age-group by sex, for each year
(1991–2008) and for three time periods: 1991–1996, 1997–2002 and 2003–2008. Age-standardized rates (ASRs) were calculated using the world standard population[16]. The average annual
percentage change (AAPC) and 95% confidence intervals (95%CI) over the 18-year study
period were calculated for each sex and cancer sites. The AAPC was estimated on fitting a Poisson regression model to the natural logarithm of the counts offset for the logarithm of the person-years, including the calendar period as a continuous variable to estimate the slope. The
calculation of the AAPC assumes that the rates increase or decrease log-linearly over the entire
period[17,18]. Graphs on time trend estimates show 3-year moving average values of rates to
minimize fluctuation due to small numbers of cases.
Results
During the 18 years of registration included in the analysis (1991–2008) a total of 12 674 cases
(5415 males and 7208 females, sex not recorded in 51) were registered. The rates of the incidence of cancer were shown to have increased in both sexes over the study period with an
AAPC of +4.8% (95% CI: 4.0–5.5) for males and +5.1% (95% CI: 4.3–5.9) for females. The ASR
for the 1991–1996 period was 102.3 per 105 in males and 102.6 per 105 in females, being 182.7
per 105 in males and 186.0 per 105 in females in the period from 2003–2008. Fig 2 shows the
age-specific incidence for all cancers in the three time periods by sex and the trends in incidence of the four most frequent tumors in males and females. In males, the most common cancers along the study period (in terms of ASRs) were those of the prostate, Kaposi’s sarcoma
(KS), the liver and the esophagus (Table 1; Fig 2C). Prostate cancer showed the most dramatic
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Fig 1. Population of Maputo by gender and age groups in the censuses of 1997 and 2007.
doi:10.1371/journal.pone.0130469.g001
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Trends in Cancer Incidence in Mozambique
Fig 2. Age-specific incidence rates of male (A) and female (B) cancers in the periods 1991–1996, 1996–2001 and 2003–2008; and trends in agestandardized incidence rates of the four most frequent cancers in males (C) and females (D) from 1991–2008.
doi:10.1371/journal.pone.0130469.g002
increase over the whole study period (AAPC +11.3%; 95% CI: 9.7–13.0), with an ASR of 61.7
per 105 in 2003–2008 (Table 1). During the study period the increase in the incidence of prostate cancer was greater in subjects over 60 years of age compared to younger subjects (35.1 per
105 versus 3.9 per 105) (Fig 3A). The age of patients with cancer of the liver varied widely, with
78.1% diagnosed in patients younger than 60 years of age (Fig 3B).
In females, the most frequent cancers over the whole study period were cancer of the uterine
cervix, breast, KS and the liver (Table 1; Fig 2D). Cancer of the uterine cervix increased along
the study period (AAPC + 4.7%; 95% CI: 3.4–6) with an ASR of 62.0 per 105 in 2003–2008
(Table 1). The increases in the incidence of both cancer of the uterine cervix and the breast
tended to be higher in women older than 40 years of age (41.9 per 105 versus 6.3 per 105 for
cancer of the uterine cervix and 16.3 per 105 versus 2.1 per 105 for breast cancer) (Fig 3C and
3D). The incidence of KS was shown to markedly increase along the study period in both gender groups and in all age groups (Fig 3E and 3F).
Among children (0–14 years) 738 cancers were registered during the 18-year study period.
Of the 738 pediatric tumors 420 (56.9%) occurred in males, 311 (42.1%) in females and in 7
cases the sex was not recorded. The most common tumors were non-Hodgkin’s lymphomas
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Trends in Cancer Incidence in Mozambique
Table 1. Age-standardized incidence rates (per 100,000) during three time periods and the average annual percentage change in age-standardized
rates in the period from 1991–2008.
MALES
Age-standardized rate per
100,000
Site
ICD-10
1991–
1996
1997–
2002
2003–
2008
Lip, oral cavity,
pharynx
C00-C14
4.6
4.0
5.0
Annual percentage
change (95%
confidence interval)
0.7% (-3.5 to 4.9)
FEMALES
Age-standardized rate per
100,000
1991–
1996
1997–
2002
2003–
2008
2.2
2.4
4.5
Annual percentage
change (95%
confidence interval)
5.5% (0.3 to 10.7)
Esophagus
C15
4.7
6.3
8.7
4.7% (1.2 to 8.2)
3.8
5.0
9.9
8.0% (4.3 to 11.8)
Stomach
C16
2.2
1.6
1.6
-3.7% (-10.4 to 3.1)
0.8
0.6
0.9
0.1% (-10.5 to 10.8)
1.9% (-3.7 to 7.5)
Colon-rectum
C18-C21
3.1
3.1
6.3
6.8% (2.2 to 11.3)
2.3
2.6
2.7
Liver
C22
18.9
9.8
14.1
-1.6% (-4 to 0.7)
7.6
4.4
8.3
2.4% (-1.1 to 5.8)
Pancreas
C25
1.9
0.8
0.4
-8.2% (-19.8 to 3.4)
0.6
1.2
0.3
-5.6% (-19.7 to 8.6)
Trachea,
bronchus, lung
C33-34
6.6
3.2
2.6
-6.1% (-10.6 to -1.6)
2.3
0.9
1.7
-2.1% (-9.1 to 4.8)
Melanoma of skin
C43
1.1
1.5
1.7
3.3% (-4.2 to 10.9)
0.7
1.3
3.3
10.6% (2.5 to 18.7)
Kaposi’s
sarcoma
C46
5.6
12.1
25.0
11.2% (8.6 to 13.8)
1.6
4.9
12.0
15.4% (11.1 to 19.6)
Other connective
and soft tissue
C49
1.5
1.9
4.4
9.6% (3.6 to 15.5)
1.2
1.3
3.1
8.1% (1.1 to 15.2)
Breast
C50
0.3
0.8
1.2
4.8% (-5.4 to 15)
13.7
12.8
26.2
6.5% (4.3 to 8.7)
Uterine cervix
C53
34.3
43.3
62.0
4.7% (3.4 to 6)
Uterine corpus
C54
2.0
3.4
3.9
4.9% (-0.3 to 10.1)
Ovary
C56
1.8
3.0
2.9
4.1% (-1.6 to 9.7)
Penis
C60
2.2
3.1
3.6
2.9% (-2.1 to 7.9)
Prostate
C61
17.4
28.2
61.7
11.3% (9.7 to 13)
Kidney
C64
0.6
0.5
0.9
4.9% (-5.8 to 15.5)
0.5
0.8
1.3
8.3% (-1.7 to 18.4)
Bladder
C67
5.8
5.1
4.0
-2.7% (-6.7 to 1.3)
7.2
4.2
2.9
-7.0% (-11.2 to -2.7)
Eye
C69
1.4
1.8
4.7
10.9% (4.9 to 16.9)
1.3
1.9
6.3
13.1% (7.4 to 18.8)
Thyroid
C73
0.2
0.5
0.6
5.3% (-9.5 to 20)
1.1
1.2
3.2
8.7% (1.2 to 16.3)
Hodgkin’s
disease
C81
0.3
0.7
1.4
-2.6% (-5.1 to -0.1)
0.6
0.2
0.7
3.5% (-0.2 to 7.2)
Non-Hodgkin’s
lymphoma
C82-C85-C96
3.8
3.9
7.7
6.4% (2.3 to 10.5)
2.1
2.8
6.0
9.0% (4 to 14)
Other
CX
20.1
17.6
28.1
3.8% (1.9 to 5.8)
14.9
16.1
23.9
3.5% (1.4 to 5.6)
doi:10.1371/journal.pone.0130469.t001
(32.5%) and KS (13.4%). Within the group of non-Hodgkin’s lymphoma, 48.9% (133/272)
were Burkitt’s lymphoma. The incidence of non-Hodgkin’s lymphoma increased from 3.6 per
106 in 1991–1996 to 20 per 106 in 2003–2008, and that of KS rose from 0.4 per 106 in 1991–
1996 to 11.0 per 106 in 2003–2008. The mean age of children with Burkitt’s lymphoma
remained constant throughout the study period (6.8–6.6 years).
Discussion
This study is one of the few reports providing solid data on cancer trends in sub-Saharan Africa
over a period of 18-years. Moreover, a major strength of this report is that data from the same
area had been previously published in Mozambique from the period from 1956 to 1961, thus
providing the unique opportunity to compare the trends in cancer for the same area over a
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Fig 3. Age-specific incidence rates of relevant cancers in the periods 1991–1996, 1996–2001 and
2003–2008. A) prostate; B) liver (males); C) uterine cervix; D) breast (females); and Kaposi’s sarcoma in
males (E) and females (F).
doi:10.1371/journal.pone.0130469.g003
long period covering almost 50 years. During this period major socio-economic and behavioral
changes have occurred in sub-Saharan Africa[4,6].
Cancer of the uterine cervix was found to be the most common cancer in women during the
whole study period with the incidence increasing at an average of 4.7% per year, being highest
at the end of the study period (ASR 62.0 per 105 in 2003–2008). These results are in agreement
with reports showing that cancer of the uterine cervix is the most common cancer in women in
sub-Saharan Africa, with the highest incidence in eastern and southern Africa[4,7,19]. The reasons for these changes are not immediately clear. The social disruption caused by the civil war
in the 1970s and 1980s may have favored the spread of human papillomavirus (HPV) infection
(as well as other sexually transmitted diseases), leading to an increased risk of cancer of the
uterine cervix. Increase in the awareness of the disease and improvements in the diagnostic
capacity may have also played a role. Indeed, HPV infection, the cause of cancer of the uterine
cervix has been shown to be highly prevalent in Mozambique with over 50% of the women
being positive at 20 years of age and 20–30% of those over 30 years of age [20–22]. As in other
low-income countries, the high prevalence of cancer of the uterine cervix may be explained by
the difficulties in carrying out secondary prevention programs due to limited resources. On the
other hand, the high prevalence of HIV infection in Mozambique has been proposed as the
most likely explanation for the increase in the incidence in cancer of the uterine cervix
observed in several sub-Saharan countries. According to the UNAIDS Global Report, the prevalence of HIV in Mozambique in people aged 15–49 was 9% in 2001[9], but was as high as 45%
in women aged 28–47 in a recent community-based study in a rural district of Maputo province[23]. However, although linkage studies of HIV/AIDS and cancer registries have indicated
a 2- to 22-fold increase in cancer of the uterine cervix in HIV-positive compared with HIVnegative women[24], the reasons for these changes are not completely understood. Moreover,
although cancer of the uterine cervix is considered to be an AIDS-defining condition, it is not
clear whether the association is simply due to the increased prevalence of infection with oncogenic HPV, as suggested by a number of studies[25,26].
Prostate cancer was found to be the most common cancer among men, with a significant
increase in its incidence (11.3% annually on average) over the 18-year study period. Prostate
cancer was rarely diagnosed in sub-Saharan Africa in the 1950s and 1960s[27,28], whereas during the period from 2003–2008 the ASR (61.7 per 105) was one of the highest observed in
Africa[5,8,29], with the greatest increase being observed in men of 60 years or over. Interestingly, prostate cancer is a major malignancy among men of African descent throughout the
world[30] and some estimations indicate that it will become the most frequent tumor in subSaharan Africa. The rise in prostate cancer in Mozambique is unlikely to be due to screening
programs based on prostate-specific antigen testing, although it is possible that increased
awareness, a greater readiness to perform prostatectomy for urinary symptoms in elderly men
and histological examination of operative biopsies might explain the increase observed in its
incidence.
The incidence of breast cancer was very low in Mozambique in the 1950s[27]. Nonetheless,
although the absolute incidence rate (ASR of 26.2 per 105 in 2003–2008) remains relatively low
by global standards[1,3,5], the incidence of breast cancer rose at a high rate annually (6.5%)
during the study period, with the greatest change occurring in postmenopausal women (Fig
3D). Part of this increase may be related to an adoption of western habits especially among the
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urban population, leading to lower fertility rates and to a higher frequency of overweight and
obesity. Although there is no information on the extent of such changes in the Maputo population, census data suggest that urban dwellers, and those with higher educational levels, have a
lower than average fertility rate[14,15]; however, it is unlikely that changes in these parameters
may be the only explanation for such as a large increase in the incidence of breast cancer over
the study period.
All cancers related to HIV infection (KS, SCC of the conjunctiva[31,32] and non-Hodgkin’s
lymphoma) showed marked annual average percentage increases (11.2% in men and 15.4% in
women for KS, 10.9% in men and 13.1% in women for cancer of the conjunctiva and 6.4% in
men and 9.0% in women for non-Hodgkin’s lymphoma). This is in keeping with the marked
increase in the prevalence of HIV infection, which in some parts of the country has reached up
to 45% among women aged 28–47 years[23]. These data are in contrast with the fall in the incidence of HIV prevalence and KS observed since the early 1990s in other sub-Saharan countries
such as Uganda [7]. No changes were observed in the age-specific incidence of KS over time
with the availability of antiretroviral therapy.
Different trends were observed in cancers traditionally considered to be frequent in Eastern
and Southern Africa in the 1950s[27]. The incidence of liver cancer showed a decrease in men
and a moderate increase in women during the study period (-1.6% and +2.4% in males and
females respectively). However, in comparison with the 1950’s a marked decrease in the incidence of liver cancer has been observed, despite the relatively high rate of chronic hepatitis B
and aflatoxin contamination of foodstuffs [33]. In spite of the viral etiology of liver cancer, the
immunosuppression caused by HIV seems to have had little or no effect on its incidence[34].
Cancer of the urinary bladder was found to be the second most frequent cancer in males and
the third in females in the period 1956–1961 with most of the cancers being SCC[27], a histological variety closely associated with urinary schistosomiasis infection[35]. Interestingly, urinary bladder cancer has shown a significant decrease, which may be related to the decrease in
the prevalence of schistosomiasis recently reported in southern Mozambique[36].
Esophageal cancer, which was an infrequent cancer in the 1950s[27] showed a marked
increase along the study period in both sexes. The reasons for this are not well understood.
Although increased alcohol intake might play a role, other factors such as dietary deficiencies
and mycotoxins have been investigated as a cause of the relatively high rates of esophageal cancer in Eastern and Southern Africa[37].
Tumors of the large bowel were relatively rare, although marked increases were observed in
both men and women. With regard to stomach cancer, though the prevalence of Helicobacter
pylori infection in adults in Maputo was high in patients with gastritis[38], this cancer was
infrequent and showed no changes in incidence during the study period.
Among children the incidence of both KS and non-Hodgkin’s lymphoma (predominantly
Burkitt’s lymphoma) significantly increased during the study period. This differs with the
decrease in the incidence of this cancer observed in other geographical areas of sub-Saharan
Africa as a result of the availability of anti-retrovirals[7,8].
A major strength of our study is that since 1991 the MCH has received virtually all the specimens from the city of Maputo during the study period and registered all the cases of cancer
based on pathological verification of the diagnosis. Special efforts have been made to maximize
the completeness of registration and ensure the quality of data. However, it cannot be ruled out
that improvement in health service coverage in the country might have contributed to the
increase of observed incidence of some cancers. In order to indicate the completeness of the
registry[39], we compared the incidence rate in different populations, and the observed similarity of these findings to those published for the period of 1991–1996 in the Kyadondo County in
Uganda support the accuracy of the current results[7]. Moreover, data from the 2012
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Trends in Cancer Incidence in Mozambique
International Agency for Research on Cancer (IARC) report in Mozambique and neighboring
countries such as South Africa are in keeping with our results [5]. The ASR on cancer of the
uterine cervix in Mozambique was 65 per 105 according to the IARC report, which is similar to
the 62 per 105 found in the last period of the study. A significant limitation of our study is that
cases of leukemia and those with only a clinical diagnosis were not registered during this
period. Another limitation is that statistics in Mozambique, as in other African countries, are
very sparse because of the lack of or the unreliability of data registration. Thus, the real incidence of cancer might be underestimated.
As has occurred in much of urban Africa, the lifestyles of the population of Maputo are
changing rapidly with the changes in the population from one comprising relatively recent
immigrants from villages, to that of second generation inhabitants, engaged in wage-earning or
informal economy, and the purchasing of foodstuffs and other necessities, rather than producing themselves[4,6]. This demographic transition is accompanied by familiar trends in patterns
of health and illness. It is therefore not surprising to note a steady increase in the incidence of
cancer.
Conclusions
In conclusion, the ongoing surveillance system provided by the cancer registry in this predominantly urban Southern African population has provided a picture of the evolution of cancer in
modern sub-Saharan Africa. Interestingly, there is a predominance of cancers of demonstrated
infectious etiology, such as HPV-associated cancer of the uterine cervix and other AIDS-related
cancers (Kaposi’s sarcoma, cancer of the conjunctiva and non-Hodgkin’s lymphomas) mirroring the increase in the HIV-AIDS epidemic in the country. To date, there is little evidence of
the onset of the epidemic of tobacco-related cancer which has been such an important feature
of the cancer profile in economically developed countries. These findings are of relevance to
guide cancer prevention policies in Mozambique and countries of similar characteristics.
Acknowledgments
The authors are grateful to the Ministry of Health of the Republica de Mozambique and Instituto Nacional de Estatística for their collaboration. We thank Donna Pringle for the English
revision of the manuscript.
Author Contributions
Conceived and designed the experiments: CL AV AG SS CM JO. Performed the experiments:
CL CC PC MI MS OA. Analyzed the data: CL AV OA AG JO. Contributed reagents/materials/
analysis tools: CL CC PC MS MI OA. Wrote the paper: CL AV AG SS CM JO.
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